The function of MCCC2 (methylcrotonyl-CoA carboxylase subunit 2, Ensembl gene identifier ENSG00000131844) is as follows. Carboxyltransferase subunit of the 3-methylcrotonyl-CoA carboxylase, an enzyme that catalyzes the conversion of 3- methylcrotonyl-CoA to 3-methylglutaconyl-CoA, a critical step for leucine and isovaleric acid catabolism. .